In communication systems in which data communication is performed between devices, techniques to transmit sub-signals (sub-data) such as a monitoring signal and control information together with a main signal (main data) such as calculation data are known.
FIG. 8 is a diagram illustrating a communication system in a conventional storage system.
The storage system illustrated in FIG. 8 includes a service controller (SVC) 600, a front-end router (FRT) 700, and two controller modules (CM) 500.
Each of the CMs 500 includes a main processing unit 501, a sub-processing unit 502, and a switch chip (SW chip) 503.
The main processing unit 501 performs calculation regarding a main signal and performs communication control of the main signal. The main processing unit 501 is a central processing unit (CPU), for example.
The sub-processing unit 502 performs calculation regarding a sub-signal and performs communication control of the sub-signal. The sub-processing unit 502 is a module management controller (MMC), for example.
The main processing units 501 of the CMs 500 are respectively connected to buses 510 through the switch chips 503, and the other ends of the buses are connected to the FRT 700. That is, the main processing units 501 of the CMs 500 are communicatively connected with each other through the switch chips 503, the buses 510, and the FRT 700.
The sub-processing units 502 of the CMs 500 are respectively connected to the SVC 600 through buses 520. That is, the sub-processing units 502 of the CMs 500 are communicatively connected with each other through the buses 520 and the SVC 600.
The bus 510 that connects the main processing units 501 through the FRT 700 is at a higher-speed than the bus 520, and a path connected through the bus 510 is referred to as in-band path. In contrast, a path connected through the lower-speed bus 520 than the bus 510 is referred to as out-band path.
The communication system illustrated in FIG. 8 is provided with the in-band path and the out-band path to realize transmission and reception of the main signal and the sub-signal.
Patent Document 1: Japanese Laid-open Patent Publication No. 2002-111596 A
However, such a conventional communication system has a large number of cables because of being provided with the in-band path and the out-band path. Therefore, for example, there is a problem that identification of a suspicious portion is complicated when a trouble occurs.